The art of producing speakers has evolved over the past decades, often involving a variety of novel transducer arrangements. Traditional speakers use a coil to induce a magnetic force based on electrical signals derived from acoustical signals. A series of such magnetic forces attract and repel the coil, and an attached cone, to and from a permanent magnet, thereby vibrating the cone to create a sound.
In contrast, electrostatic speakers, which is synonymous with electrostatic loudspeakers (ESLs), utilize a thin diaphragm, or membrane, to produce a sound. This membrane is placed under tension. Typically this membrane has a coating, such as aluminum or graphite, on one side that will hold an electrostatic charge when supplied with a high voltage. One or more stators are spaced adjacent to the faces of the membrane. A stator is an electrically conductive stationary plate that, when charged, attracts or repels the charged membrane, thereby causing the membrane to move to produce sound. Insulating spacers separate the one or more stators from the membrane. These spacers must maintain a critical distance, close enough for the stators to exert a sufficient force to move the membrane, and far enough to prevent the membrane surface's high voltage from discharging onto the stator or another nearby component either through contact or jumping of charge. An amplified electrical signal drives each stator, which variably and alternately attract or repel the charged membrane, causing the membrane to move, respectively, toward or away from the respective stator. Typically, one stator is placed to each side of the membrane, so the force applied over the distance the membrane moves stays relatively constant, thereby avoiding distortion of the resulting sound over a range of frequencies. Two sources of information about electrostatic speakers, which are incorporated herein by reference, are:                1. Electrostatic Loudspeaker Design and Construction, 2nd Edition, Ronald Wagner, Audio Amateur Publishers, Peterborough, N.H. (1993, ISBN 0-9624-191-6-8).        2. The Electrostatic Loudspeaker Design Cookbook, 1st Edition, Roger R. Sanders, Audio Amateur Publishers, Peterborough, N.H. (1995, ISBN 1-882580-00-1).        
Specially designed speakers have been described in the commercial and patent literature. For instance, a commercially available electrostatic speaker, made by MartinLogan, utilizes a diaphragm, spacers on each side, and curved stators peripherally, where the stators have numerous small holes. The speakers produce audible sound reported to have exceptional linearity and low distortion. These speakers can be several feet high, demonstrating suitable spacer placement over a large speaker area. Descriptions of other related devices can be found in U.S. Pat. Nos. 5,239,589, 5,682,290 and 5,889,871.
The present invention represents an improvement in the art of production of ESLs by incorporating at least one printed circuit board (PCB) into an ESL, and by using a combination of features in conjunction with the PCB to manufacture ESLs with reproducible tolerances, leading to improved precision and performance. The invention also is well suited for mass-production and scale-up techniques.